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Disorders ofMemory

You have to begin to lose your memory, if only inbits and pieces, to realize that memory is whatmakes our lives. Our memory is our coherence,our reason, our feeling, even our action. Withoutit, we are nothing. (Luis Buñuel)

What Is Memory?

Dynamic and malleable; goes forward andbackward in time

Forms the basis of experience andperceptions of the self

Often taken it for granted because it’smost noticeable when it’s not working

Multiple memory systems and processes But memory is not like a VCR

Memory Schematic

Recall/Recognition

Working Memory

Short term storage Consolidation

SensoryBuffers

Retrieval

Long TermStorageEncoding

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Taxonomy of LTM

Episodic SemanticPriming Procedural

LTM

Explicit / DeclarativeImplicit

Conditioning

Memory Problems

Classic Cases: H.M.

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Classic Cases: N.A. Left dorsomedial nucleus of the thalamus Similar pattern of deficits to H.M. Retrograde amnesia - 2 years Almost complete anterograde amnesia Verbal memory < visual memory (though

both affected)

Classic Cases

What functions may be left intact in casesof severe amnesia? Immediate memory – can recite back several

words immediately (amnestic after 5 min.) Procedural memory Intact memory for very remote events Other facets of functioning

Personality Intelligence

Declarative Memory Functional Model

Sensory information sent to memoryprocessing areas (hippocampus, etc.)

Return pathways “store” memories back inoriginal cortical regions

Neural substrates for this model Medial temporal lobes Diencephalon (thalamus and hypothalamus) Basal forebrain

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http://www.driesen.com/memory_in_the_brain.htm

Declarative Memory

Medial Temporal Structures Center around the hippocampal formation Hippocampal formation includes:

The hippocampus proper The dentate gyrus The subiculum

The adjacent entorhinal, perirhinal, andparahippocampal cortices are important too

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Declarative Memory

Diencephalic Structures Anterior and dorsomedial nuclei of the

thalamus Mammillary bodies of the hypothalamus Dorsomedial thalamic nuclei and mammillary

bodies are often implicated in Wernicke-Korsakoff’s disease

Declarative Memory

Basal Forebrain Structures A major source of cholinergic output to the

cortex; projects to the medial temporal lobes The basal forebrain memory structures include:

The nucleus basalis of Meynert The substantia innominata The medial septal nucleus The nucleus of the diagonal band of Broca

Damage results in prominent anterogradeamnesia and confabulation

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Hippocampus

MammillaryBodies

AnteriorThalamus

CingulateGyrus

Fornix

MamillothalamicTract

Bauer, Grande, & Valenstein, 2003

Papez Circuit

• Major declarativememory system

• Important forconsolidation

Declarative Memory

Declarative MemoryOrganization

Corresponds to traditional ideas ofhemispheric lateralization Dominant (usually left) lesions typically cause

deficits in verbal memory Nondominant (usually right) lesions typically

lead to deficits in visual-spatial memory

Declarative Memory

Frontal lobe contributions to memory Strategy formation Left: Storage; Right: Retrieval Metamemory and memory monitoring

Knowledge of memory processes Knowledge of memory contents Memory for self-generated responses

Working memory

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Central executivePhonological loop

Visuo-spatial sketchpad

Working Memory

A concept popularized by Alan Baddeleyin the 1980’s Three components:

Research of Patricia Goldman-Rakic Points to the dorsolateral prefrontal cortex as

critical for working memory

Non-Declarative (Implicit)Memory

Memory outside of the limbic circuitryalready discussed Different types:

Implicit priming (e.g., ‘parachute’ primes par____) Preserved in Korsakoff’s patients

Procedural and motor skill learning Preserved in H.M.

Habit memory (conditioning) Preserved in many amnesics

Brain structures: Cerebellum, basal ganglia, and motor strip

Examples of Memory Research Are there anatomically separate systems for different

kinds of LTM (e.g., declarative versus nondeclarative)? How can we gather evidence of separate systems? Double dissociation for nondeclarative perceptual-motor

tasks versus declarative verbal memory tasks

Huntington’s patients(progressive deterioration ofcaudate nucleus of basal ganglia)↑ verbal memory, ↓ perceptual-motor

Alzheimer’s patients(progressive deterioration ofmedial temporal structures)↑ perceptual-motor, ↓ verbal memory

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Associative completionpriming

Word completionpriming

Trace conditioningDelay conditioning

ImpairedIntact

Schachter (1988) Explicit vs. implicit memory Performance of amnesics on memory tasks

Some tasks are learned implicitly, i.e. they do notappear to require intact MTL structures and do notrequire awareness

Conscious awareness (likely relying on MTL structures)is necessary for some types of priming and conditioning

Disorders Affecting Memory Dementias (e.g., Alzheimer’s disease) Toxic conditions Anoxia or hypoxia Infarcts Wernicke-Korsakoff’s syndrome Head injury/TBI Seizures Transient global amnesia Psychogenic amnesia

“Normal” memory loss

Infantile amnesia – inability to recallevents from the first 1-3 years of life

Mild decline in memory function with age(contrast with dementia)

Forgetting with the passage of time Loss of memory immediately after

awakening from sleep

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Memory Assessment

Testing Specific Aspects of Memory Evaluate adjunct processes

(e.g., attention) Evaluate clinically relevant dimensions

Encoding, Storage, Retrieval Immediate vs. Delayed Recall Recall vs. Recognition

Recognition is easier than free recall for intact and brain-injured individuals

Material specificity (verbal vs. nonverbal)

Informal Memory Assessment Simple Bedside Tests of Memory Attention, working memory

e.g., digit span Brief time scale, must be intact for encoding

Immediate/delayed memory Provide information and ask for it to be recalled

and then again after 5-30 minutes Remote memory

Ask about verifiable personal information orabout well-known events or figures in the past

Neuropsychological Tests

Wechsler Memory Scale (WMS-III) Visual, Verbal, and Global memory measures

California Verbal Learning Test (CVLT-II) Word list learning task

Rey-Osterreith Complex Figure Visual memory